Ribulose bisphosphate carboxylase/oxygenase activase is an enzyme localized to chloroplasts which activates Rubisco by promoting ATP-dependent conformational changes. Alternative name: RuBisCo activase RCA. There are two forms of activase (alpha and beta) in some species (for example Arabidopsis, camelina, spinach, rice) and only one form in other species (tobacco, maize,?Chlamydomonas). Alpha is about 46-47 kDa, beta is about 42 kDa. Species that have only one form have the beta form.
